Ponytail

He says nothing. He writes one line. It works.

You know him. Long ponytail. Oval glasses. Has been at the company longer than the version control. You show him fifty lines; he looks at them, says nothing, and replaces them with one.

Ponytail puts him inside your AI agent.

Before / after

You ask for a date picker. Your agent installs flatpickr, writes a wrapper component, adds a stylesheet, and starts a discussion about timezones.

With ponytail:

<!-- ponytail: browser has one -->
<input type="date">

More survivors in examples/.

How it works

Before writing code, the agent stops at the first rung that holds:

1. Does this need to exist?   → no: skip it (YAGNI)
2. Stdlib does it?            → use it
3. Native platform feature?   → use it
4. Installed dependency?      → use it
5. One line?                  → one line
6. Only then: the minimum that works

Lazy, not negligent: trust-boundary validation, data-loss handling, security, and accessibility are never on the chopping block.

Install

The most effort ponytail will ever ask of you:

/plugin marketplace add DietrichGebert/ponytail
/plugin install ponytail@ponytail

That was it. He'd be proud. He won't say it.

Active every session. /ponytail-review finds what to delete in your diff. /ponytail ultra exists for when the codebase has wronged you personally. /ponytail-help explains the rest.

Cursor, Windsurf, Cline, Copilot, Aider: copy the matching rules file from this repo (.cursor/rules/, .windsurf/rules/, .clinerules/, .github/copilot-instructions.md, AGENTS.md).

FAQ

Does it need a config file?
No.

What if I really need the 120-line cache class?
You don't. Insist anyway and he'll build it — slowly, correctly, while looking at you.

Does it scale?
The code you never wrote scales infinitely. Zero bugs, zero CVEs, 100% uptime since forever.

Why "ponytail"?
You know exactly why.

Numbers

5 coding tasks, same agent with and without ponytail: −16% tokens, ~4× faster, 293 → 47 lines. The 246 lines nobody wrote have never caused an incident. Data: benchmarks/.

License

MIT. The shortest license that works.